The subsequent ruckus has focused on an alleged cover-up of the outbreak. The more important message, though, is how easily TB can get out of control even in the richest country, and how, unless we are very careful, economic recession could make that much worse.

In June, the CDC reported how this outbreak started: a schizophrenic man visited psychiatric clinics around Jacksonville over five months in 2008, complaining of a cough. On the fourth visit he was finally diagnosed with TB. But he refused to stay on his TB drugs, which you need to take for months before you are no longer contagious. So he was locked up in the state TB hospital.

By then, however, he had already spread the infection. In 2009 CDC found TB infections in an "extraordinary" 88 per cent of his contacts in the mental health facility he attended. The normal transmission rate is between 20 and 30 per cent.

Hard to trace

The CDC could not track all the cases and treat them, so the spread continued, and last February, Jacksonville called them in again. The CDC has now traced 99 cases since 2004, mainly in homeless shelters.

Of 3222 recent contacts of these cases, the CDC traced only 253. If only the usual third or so of contacts were infected, that means around 1000 people are still spreading the strain. The outbreak, CDC concluded, "has yet to show signs of abating".

So why is Florida cutting public health spending and closing the TB hospital? It is partly due to small-government ideology and partly to budget worries. But it is also true that overall TB cases in Florida have been declining – down nearly two-thirds from a peak in 1994.

However, beneath the overall decline, these TB bacteria, in this particular human network of contagion, are booming: there were 10 cases in 2010, 38 in 2011, and six in the first two months of 2012. The CDC fears this will result in the kind of TB explosion seen in homeless communities elsewhere.

"As overall incidence declines, micro-epidemics become more important," as do delays in diagnosis by doctors who rarely see TB, says Giovanni Migliori, head of the World Health Organization's TB centre in Tradate, Italy.

Secondly, TB anywhere is TB everywhere. Florida officials say they didn't alert the public to the outbreak as they didn't want to subject homeless people to further stigma. Fair enough, but this outbreak may not be limited to the homeless: the CDC found no history of homelessness, jail or drug use in 21 of the 99 cases it found. In 29 cases, the CDC could not trace the source of infection to the homeless community.

Meanwhile, TB among the homeless does not remain there. Such outbreaks, as in New York in the 1990s, breed drug-resistant TB as it is hard to ensure marginalised people stay on their medication for months. Every new resistant case makes the global epidemic harder to fight.

It sounds callous and immoral to imply that we should care about an outbreak among the impoverished because it eventually affects the non-impoverished – but in New York, says Migliori, there was little action until it became clear that the more affluent were affected. So let's be clear: this will happen unless we pay attention now and avoid making public health cuts that will cost dearly later.

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